FIGS. 5 through 7 respectively illustrate examples of conventional joint devices. Of these, FIG. 5 represents a conventional device which supplies a projection nut 1 to an objective steel plate (not shown) by operating a supply rod 2. The supply rod 2 is movably accommodated in a guide tube 3. A guide pin 4 is secured to the tip of the supply rod 2. Although not shown, the supply rod 2 is linked with a piston rod of a pneumatic cylinder.
A parts-supply tube 5 is connected to the bottom end of the guide tube 3 via welding. As shown in FIG. 6, the parts-supply tube 5 is of rectangular section, and yet, it bends in the direction of the bottom line. An outlet aperture 6 is provided along the bottom edge of the parts-supply tube 5 creating an opening and the bottom space is closed by a stopper plate 7 shown to the right of FIG. 5. A permanent magnet 8 is built in the stopper plate 7 in order to attract the nut 1 so that it can provisionally be held in contact with the stopper plate 7. An arm 9 is externally welded to the guide tube 3. A bolt 10 threaded through the arm 9 forces the stopper plate 7 against the guide tube 3 so that the stopper plate 7 can be secured to the guide tube 3. A joint tube 11 is connected to the upper edge of the parts-supply tube 5 via welding. A plastic-made supply hose 12 is tightly inserted in the joint tube 11.
Another example of a conventional joint device shown in FIG. 7 has a joint tube 13 which is provided with a large-diametric dimension 15 and a small-diametric dimension 16 across a boundary step 14 created by tightly inserting a supply hose 17 and a parts-supply tube 18 through tube 13. The joint tube 13 is coupled with a stationary member via a fixing member 19 represented by dashed lines.
Nevertheless, according to the conventional structure shown in FIG. 5, since the supply hose 12 is merely inserted in the joint tube 11, the supply hose 12 is apt to shake itself loose. In an extreme case, the supply hose 12 may be disengaged from the joint tube 13. If an unwanted bending moment acts upon the supply hose 12, then a stepped section may be generated at the boundary between the supply hose 12 in the inner passageway and the parts-supply tube to result in an obstruction to smoothly transfer the nut 1. Likewise, even when the supply hose 12 is withdrawn slightly clearance is generated to also obstruct smooth delivery of the nut 1. Likewise, although the supply hose 17 must precisely be engaged with the parts-supply tube 18 at the boundary step 14, according to the conventional structure shown in FIG. 7, if the coupling position deviates to the left of the joint device shown in FIG. 7 by the slightest amount, then, it will cause an unwanted bending moment to be generated which would merely result in an obstruction to smoothly transfer the nut 1 as in the above cases. Furthermore, since the joint tube 13 is necessarily manufactured by molding means, it is by no means advantageous in terms of the production cost.